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Kepler, Johannes

planetary motion sun laws

(1571–1630) German astronomer and physicist: discovered laws of planetary motion.

Kepler had smallpox at the age of 3, damaging his eyesight and the use of his hands, which makes his achievements, as the son of a mercenary, the more remarkable. Kepler read and approved the work of while studying theology at Tübingen, intending originally to go into the church. He became a teacher of mathematics in the Protestant Seminary at Graz in Austria. In 1600, having been forced to leave his teaching post due to the religious persecution of Protestants, he was invited to join in Prague, who assigned him the task of working out the orbit of Mars. Brahe died 2 years later, leaving Kepler his 20-year archive of astronomical observations. In 1609, having failed to fit Brahe’s observations of Mars into the perfectly circular orbits of the Copernican cosmology, he formulated Kepler’s first two laws of planetary motion: that planets follow elliptical orbits with the Sun at one focus and that the line joining a planet to the Sun, as it moves, sweeps through equal areas in equal times. At last understanding the principles of planetary motion, Kepler then proceeded with the more onerous but valuable task of completing the ‘Rudolphine Tables’, the tabulation of Brahe’s results for his sponsor Emperor Rudolph, a job which he did not complete until 1627. A fine scientist, he was also a mystic and astrologer, cast horoscopes and believed in the ‘music of the spheres’ (from the planets).

In 1611 civil war broke out, Rudolph was deposed and Kepler’s wife and child died. He moved to Linz, where he propounded his third law of planetary motion: that the squares of the planetary periods are proportional to the cubes of their mean distances from the Sun. These three laws gave a sound basis for all later work on the solar system. Kepler also wrote a book on the problems of measuring the volumes of liquids in wine casks that was to be influential in the evolution of infinitesimal calculus.

Kerger, Paula A. - President and Chief Executive Officer of Public Broadcasting Service, Career, Sidelights [next] [back] Kenter, Yildiz (1928–) - PERSONAL HISTORY, BIOGRAPHICAL HIGHLIGHTS, PERSONAL CHRONOLOGY:, INFLUENCES AND CONTRIBUTIONS, THE WORLD’S PERSPECTIVE, LEGACY

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